I read somewhere that if some of your sites perform badly it effects the sites that perform well? So if I take off the ads I have on some in-dev sites it would raise the revenue made from the ones that are making more..
if you have noticed a sudden major drop in the pay per click on ALL of your sites then you may want to atempt to take the culprate site off of your account. If you had all your sites getting let's say .40 a click or so and one of your sites you knew all the people were clicking on the ads on accident. Then all of the sudden your pay drops down to .05 a click and stays there for a while then I'd try to take the bad site off. See if your other sites go back up to .40 or so. If they were all .05 from the beginning then you are probably in a bad or low paying niche. If this is the case I'd try to get a ton of volume to make up for the low paying clicks.
Problem is that since smartpricing is recalculated on a weekly basis or so it's no quick procedure to find out which site is causing it, unless it's obvious.